DNA Sequences coding for PTH variants, PTH variants, expression vector, bacterial host, use and therapeutic composition

ABSTRACT

The invention relates to DNA sequences coding for PTH variants, to PTH variants, expression vectors, bacterial hosts, uses and therapeutic compositions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to analogs of parathyroid hormone.

2. Brief Description of Related Art

Parathyroid hormone (PTH) regulates the level of calcium in blood plasma by exerting, inter alia, anabolic and catabolic effects on the skeleton and also by promoting calcium re-absorption by the kidneys. There is reason to believe that the bone-building effect of PTH can be exploited for the clinical treatment of osteoporosis; see J. Bone Mineral Res., 1 (1987) 377-382.

There are also indications that the multiple functions of PTH are exerted by different regions of the hormone molecule. For example, it has been found that the N-terminal 34 amino acids mediate the binding of the hormone to its kidney cell receptor with subsequent stimulation of adenylate cyclase (see Adv. Prot. Chem., 32 (1982) 323-395) but that a mitogenic effect originates from the central region sequence 28-48 (see DE-A-37 25 319.0) which effect is not mediated by adenylate cyclase but possibly by protein kinase C. It would therefore seem attractive to modulate individual hormone effects by controlled variation of the amino acid sequence of PTH or of PTH fragments and thus possibly to reduce the catabolic activity of the hormone or increase its anabolic activity.

With regard to the prior art, reference should also be made to U.S. Pat. Nos. 4,086,196 and 4,423,037 and John et al., in Adv. Prot. Chem., 32 (1982) 323.

SUMMARY OF THE INVENTION

For the above purpose, according to the invention a DNA sequence is provided that codes for a variant of PTH(1-84), in which

one or two amino acids is/are exchanged for another amino acid in the region of positions 1 to 27, and which

is optionally lengthened N-terminally (position +1) by one or two amino acids and is optionally also shortened C-terminally (position +84) by one or more amino acids or

is optionally shortened C-terminally (position +84) by one or more amino acids,

the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.

According to a further embodiment, a DNA sequence is provided that codes for a variant of PTH(1-84), in which

one or two amino acids is/are exchanged for another amino acid in the region of positions 28 to 31, and which

is optionally lengthened N-terminally (position +1) by one or two amino acids and is optionally also shortened C-terminally (position +84) by one or more amino acids or

is optionally shortened N-terminally (position +1) and/or C-terminally (position +84) by one or more amino acids,

the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.

According to a further embodiment, a DNA sequence is provided that codes for a variant of PTH(1-84), in which

one or two amino acids is/are exchanged for another amino acid in the region of positions 32 to 34, except that tyrosine may not appear at position 34, and, further, which

is optionally lengthened N-terminally (position +1) by one or two amino acids and is optionally also shortened C-terminally (position +84) by one or more amino acids or

is optionally shortened N-terminally (position +1) and/or C-terminally (position +84) by one or more amino acids,

the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.

According to a further embodiment, a DNA sequence is provided that codes for a variant of PTH(1-84), in which

one or two amino acids is/are exchanged for another amino acid in the region of positions 30 to 34, and which

is optionally lengthened N-terminally (position +1) by one or two amino acids and is optionally also shortened C-terminally (position +84) by one or more amino acids or

is optionally shortened N-terminally (position +1) and/or C-terminally (position +84) by one or more amino acids,

the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.

According to a further embodiment, a DNA sequence is provided that codes for a variant of PTH(1-84), in which

(a) the region of positions 28 to 34 and especially 30 to 34 is unchanged or

(b) one or two amino acids is/are exchanged for another amino acid in the region of positions 28 to 34 and especially 30 to 34 and,

in addition to (a) or (b), one or two amino acids is/are exchanged for another amino acid outside the region of positions 28 to 34 or 30 to 34, and which

is optionally lengthened N-terminally (position +1) by one or two amino acids and is optionally also shortened C-terminally (position +84) by one or more amino acids or

is optionally shortened N-terminally (position +1) and/or C-terminally (position +84) by one or more amino acids,

the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.

The DNA sequence preferably codes for a PTH variant whose N-terminus is lengthened by proline. Also preferred are hPTH, bPTH, pPTH, rPTH and cPTH variants. As regards the numbering of the DNA sequences, 1 denotes the first nucleotide of the first PTH codon so that the numbers to be found in the following Table 1 denote the position of the first nucleotide shown in relation to the first nucleotide of the first PTH codon.

According to a further embodiment, the invention relates also to PTH variants that are coded by one of the above described DNA sequences, and especially variants of human (h), bovine (b), porcine (p), rat (r) and canine (c) PTH.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

The PTH variants according to the invention can be formally classified in the following four groups.

Group 1: conservative amino acid exchanges in positions 27 and 29 that maintain the stimulation both of adenylate cyclase and of DNA synthesis ("functional PTH equivalents"); Examples: Q29N; K27R.

Group 2: non-conservative amino acid exchanges (variations with charge reversal or cancellation, change of hydrogen bridges, reversal of hydrophobicity) in regions 29 to 31 or 33 to 34 and also exchanges in position 32 that result in a significant reduction in the stimulation of DNA synthesis and in a substantial retention of the effect on adenylate cyclase; Examples Q29A, H32L, H32K, H32R.

Group 3: non-conservative amino acid exchanges (as defined above) in region 1 to 27 that result in a significant reduction in adenylate cyclase stimulation and in some cases increase DNA synthesis or leave it unaffected. Examples of increase in DNA synthesis: E4R, E4R/R20E, K13P, K27L; Example of unaffected DNA synthesis: R20E.

Group 4: non-conservative amino acid exchanges in region 1 to 27 that maintain the stimulation of adenylate cyclase but reduce that of DNA synthesis; Example: L11K.

Finally, the invention relates to hybrid peptides that include a PTH variant according to the invention, to expression vectors for the expression of the proteins according to the invention, bacterial hosts, such as E. coli, for the expression vectors, the use of the DNA sequences for the preparation of the peptides according to the invention, and therapeutic compositions that contain those peptides. DE-A-37 25 319.0 and DE-A-37 25 320.4 are relevant prior art.

The invention is explained in more detail below by an Example and two Tables.

EXAMPLE

The expression plasmid pEX-pPTH of DE-A-37 25 319.0 was used as starting material. A BamHI/SstI fragment of this plasmid 123 base pairs long was recloned into phage vector M13mp18. Using this phage vector and using synthetic oligonucleotides, the mutants listed in Table 1 were prepared in accordance with the gapped-duplex-method (Methods Enzymol., 100 (1983) 468-500).

After back-cloning the mutated PTH partial genes into the expression vector, the corresponding variant Cro-β-galactosidase-hPTH-fusion proteins were expressed, purified and cleaved; the PTH variants freed in that manner were purified in accordance with DE-A-37 25 319.0 and DE-A-37 25 320.4. Purification by means of carboxymethylcellulose was carried out batchwise. Subsequent purification by reversed-phase HPLC yielded homogeneous material.

The PTH variants so obtained were tested for their ability to stimulate adenylate cyclase in isolated membranes of porcine adrenal cortices in an in vitro test according to Mohr and Hesch (Biochem. J., 188 (1980) 649-656).

They were also tested for their ability, according to DE-A-37 25 319.0 and DE-A-37 25 320.4, to increase the DNA synthesis of embryonal chicken chondrocytes.

The results obtained are compiled in Table 2.

    ______________________________________                                         Materials                                                                      ______________________________________                                         pEX           Genofit Heidelberg                                               M13mp18       GIBCO BRL                                                        hPTH gene     P 33 12 928.2                                                    bPTH gene     PNAS, 78 (1981) 7365                                             pPTH gene     Nucleic Acids Res., 15 (1987)                                                  6740                                                             rPTH gene     Nucleic Acids Res., 15 (1987)                                                  6740                                                             cPTH gene     J. Bone Mineral. Res., 3                                                       (Suppl. 1) (1988) Poster No. 309                                 ______________________________________                                    

The PTH genes mentioned can be prepared using peptide synthesis apparatus.

                                      TABLE 1                                      __________________________________________________________________________     Mutations in the hPTH gene and resulting PTH variants                          Name   DNA sequence       AA exchange                                          __________________________________________________________________________     E4R    AGT AGA ATT        Glu (4) -> Arg (4)                                          28                                                                      L11K   AAC AAG GGA        Leu (11) -> Lys (11)                                        31                                                                      G12A   CTC GCG AAA        Gly (12) -> Ala (12)                                 G12P   CTC CCG AAA        Gly (12) -> Pro (12)                                        34                                                                      K13P   GGC CCA CAT        Lys (13) -> Pro (13)                                 K13S   GGC TCC CAT        Lys (13) -> Ser (13)                                 K13L   GGC CTG CAT        Lys (13) -> Leu (13)                                 G12N, K13S                                                                            AAT TCC CAT        Gly (12), Lys (13) ->                                                                      Asn (12), Ser (13)                              55                                                                      R20E   GAG GAA GTA        Arg (20) -> Glu (20)                                        7         55                                                            E4R, R20E                                                                             AGT AGA ATT. .                                                                           GAG GAA GTA                                                                             Glu (4), Arg (20) ->                                                                       Arg (4), Glu (20)                               76                                                                      K27L   AAG CTT CTG        Lys (27) -> Leu (27)                                 K27R   AAG CGT CTG        Lys (27) -> Arg (27)                                        82                                                                      Q29A   CTG GCA GAT        Gln (29) -> Ala (29)                                 Q29N   CTG AAC GAT        Gln (29) -> Asn (29)                                        91                                                                      H32L   GTA CTC AAT        His (32) -> Leu (32)                                 H32R   GTG CGC AAT        His (32) -> Arg (32)                                 H32K   GTG AAG AAT        His (32) -> Lys (32)                                 H32S   GTT TCG AAT        His (32) -> Ser (32)                                 __________________________________________________________________________      The numbering at the DNA sequences indicates the position of the first         nucleotide shown in relation to the first nucleotide of the first PTH          codon (=1). The underlined bases have been changed in relation to the          recombinant wild type. The position numbers of the exchanged amino acids       refer to the first amino acid of human parathyroid hormone (Ser (l)).    

                  TABLE 2                                                          ______________________________________                                         Relative activity of the PTH variants on renal                                 adenylate cyclase and DNA synthesis in chondrocytes                                        Adenylate cyclase                                                                           DNA synthesis                                         PTH-variant (%)          (%)                                                   ______________________________________                                         rec-hPTH    100          100                                                   Q29N        99           95                                                    K27R        90           81                                                    Q29A        104           8                                                    H32L        93           11                                                    H32R        87           36                                                    H32K        85           22                                                    L11K        89           21                                                    E4R         47           88                                                    K27L        35           70                                                    E4R, R20E   20           58                                                    K13P         6           88                                                    R20E         0            0                                                    ______________________________________                                          All the PTH variants, like the wild type, are lengthened Nterminally by        one proline residue. All the activities are relative to that of the            recombinant hPTH and indicate the ability of the respective variant to         stimulate either cyclase or DNA synthesis beyond the base level.          

We claim:
 1. DNA sequence that codes for a variant of PTH(1-84), in whichone or two amino acids are exchanged for another amino acid in the region of positions 28 to 31, and which is optionally lengthened N-terminally (position +1) by one or two amino acids the amino acids coded by the DNA sequence not being arranged in an order that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 2. DNA sequence that codes for a variant of PTH(1-84), in whichone or two amino acids are exchanged for another amino acid in the region of positions 32 to 34, except that tyrosine may not appear at position 34, and, further which is optionally lengthened N-terminally (position +1) by one or two amino acids or is shortened C-terminally (position +84) by one amino acid or is optionally shortened N-terminally (position +1) and C-terminally (position +84) by one amino acid, the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 3. DNA sequence that codes for a variant of PTH(1-84), in whichone or two amino acids are exchanged for another amino acid in the region of positions 30 to 34, except that tyrosine may not appear at position 34, and which is optionally lengthened N-terminally (position +1) by one or two amino acids or is shortened C-terminally (position +84) by one amino acid, or is optionally shortened N-terminally (position +1) and C-terminally (position +84) by one amino acid, the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 4. DNA sequence that codes for a variant of PTH(1-4), in which(a) the region of positions 28 to 34 is unchanged or (b) one or two amino acids are exchanged for another amino acid in the region of positions 28 to 34 except that tyrosine may not appear at position 34 and, in addition to (a) or (b), one or two amino acids are exchanged for another amino acid outside the region of positions 28 to 34, and which is optionally lengthened N-terminally (position +1) by one or two amino acids the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 5. DNA sequence that codes for a variant of PTH(1-84), in whichone or two amino acids are exchanged for another amino acid in the region of positions 32 to 34, except that tyrosine may not appear at position 34, the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 6. DNA sequence that codes for a variant of PTH(1-84), in whichone or two amino acids are exchanged for another amino acid in the region of positions 30 to 34, except that tyrosine may not appear at position 34, the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 7. DNA sequence that codes for a variant of PTH(1-84), in which(a) the region of positions 28 to 34 is unchanged or (b) one or two amino acids are exchanged for another amino acid in the region of positions 28 to 34 except that tyrosine may not appear at position 34 and, in addition to (a) or (b), one or two amino acids are exchanged for another amino acid outside the region of positions 28 to 34 the amino acids coded by the DNA sequence not being arranged in a sequence that occurs in bPTH, pPTH, rPTH, cPTH or hPTH.
 8. DNA sequence according to any one of claims 1, 2, 3, or 4 which codes for a PTH variant that is lengthened N-terminally by proline.
 9. A DNA sequence according to claims 4 or 7, wherein said region is of positions of 30 to
 34. 10. Bacterial expression vectors having a DNA sequence according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 9 for the expression of a peptide in a bacterial host.
 11. A DNA sequence according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 9, which codes for a variant protein of hPTH, bPTH, pPTH, rPTH or cPTH.
 12. Bacterial host having an expression vector according to claim
 10. 13. Bacterial expression vectors according to claim 10 wherein Escherichia coli is the bacterial host. 